The problem is solved.
There was my error in /etc/mail/sendmail.mc
in the following line:
INPUT_MAIL_FILTER(`spamassassin', `S=local:/var/run/spamass-milter/spamass-milter.sock, F=T, T=C:15m;S:5m;R:5m;E:10m')dnl

I was missed an opening quote in (`spamassassin', S=local:/var/run/spamass-milter/spamass-milter.sock, F=T, T=C:15m;S:5m;R:5m;E:10m')dnl
Sendmail accepted local socket parameter, but skipped others.
The main thing was that Sendmail skipped parameter F=T, which defines reaction when Milter returns error.